The present invention relates to cationic sugar surfactants with improved biodegradability that can be used as hydrotropes for surfactants, especially for nonionic alkylene oxide adducts in alkaline solutions, and as cleaners for hard surfaces. They are obtained from ethoxylated quaternary ammounium compounds and reducing saccharides or alkyl glycosides.
Surface active nonionic alkylene oxide adducts are widely used as essential degreasing and/or dispersing components in alkaline cleaning compositions. Their solubility in cleaning composition concentrates is, however, limited in the presence of high amounts of electrolytes, such as alkali and/or alkaline complexing agents.
It is prior known that cationic surfactants, such as ethoxylated fatty amines (about 14-20 moles ethylene oxide per mol fatty amine) that have been quaternized by an alkylating agent, e.g. methyl chloride or dimethyl sulfate, are excellent hydrotropes for nonionic alkylene oxide adducts and are also good cleaners themselves. However, from an environmental point of view they are less desirable, since they are not readily biodegradable.
The main purpose of the present invention is to provide products that are excellent hydrotropes for surfactants.
Another purpose is to provide hydrotropes with improved biodegradability over the prior used cationic surfactants.
Still another purpose is to provide hydrotropes which contribute to the cleaning performance of the surfactants.
It has now been found that said main purpose is achieved by using, as a hydrotrope a cationic sugar surfactant containing at least one hydrocarbon group with 6-24 carbon atoms and at least one quaternary ammonium group where at least one substituent is an alkyleneoxy containing group which is connected to a saccharide residue by a glycosidic bond.
The present invention generally relates to a cationic sugar surfactant containing at least one hydrocarbon group with 6-24 carbon atoms and at least one quaternary ammonium group where at least one substituent is an alkyleneoxy containing group which is connected to a saccharide residue by a glycosidic bond, and more particularly, the use of said sugar surfactant as a hydrotrope for surfactants.
In accordance with the present invention, new hydrotropes which contribute to the cleaning performance of the surfactants have been found. These hydrotropes comprise a cationic sugar surfactant containing at least one hydrocarbon group with 6-24 carbon atoms and at least one quaternary ammonium group where at least one substituent is an alkyleneoxy containing group which is connected to a saccharide residue by a glycosidic bond.
Preferably the substituent has the formula (AO)s(G)g where AO is an alkyleneoxy group with 2-4 carbon atoms, G is a saccharide residue, g is a number from 1 to 10 and s is a number from 1 to 12.
The cationic sugar surfactant according to the invention may be produced by reacting
a) an amine compound containing at least one hydrocarbon group with 6-24 carbon atoms and at least one quaternary ammonium group, where at least one substituent is a hydroxyalkyl containing group, and
b) a reducing saccharide or an alkyl glycoside where the alkyl group has 1-8 carbon atoms, at least partially in the presence of an acid. The substituent attached to the quaternary ammonium group has preferably the formula (AO)s(G)g, where AO is an alkyleneoxy group with 2-4 carbon atoms, G is a saccharide residue, g is a number from 1 to 10 and s is a number from 1 to 12.
Suitable sugar surfactants according to the invention have the formula 
where R is an aliphatic group with 6-24, preferably 8-20 carbon atoms; R1 is an aliphatic group with 1-4 carbon atoms or (AO)s(G)p; R2, R3 and R4 are a group (AO)s(G)p, an aliphatic group with 1-24 carbon atoms or a hydroxyalkyl group with 2-4 carbon atoms; AO is an alkyleneoxy group with 2-4 carbon atoms; s is 0-12, preferably 1-6 and xcexa3 s=1-25, preferably 3-15; G is a saccharide residue which is connected to the rest of the molecule by a glycosidic bond and p (the degree of polymerisation) is 0-10 and xcexa3 p=1-20; r=0-3; y=2-3; X=CO or COO(AO)t(CqH2q) or O(AO)t(CqH2q); n=0 or 1; n1 is 0 except when X is CO, then n1 is 1; q=2-4; t=0-2; u=0 or 1 and v=0 or 1, provided that the sum (v+xcexa3 u) is 1-3, preferably 1; Z is an anion, preferably a monovalent anion, such as Clxe2x88x92 or methyl sulphate and z is the charge of the anion Z. The nitrogen atoms where u or v is 1 are quaternary and thus have a permanent positive charge. These cationic sugar surfactants have, in comparison with the prior known cationic hydrotropes, an essentially improved biodegradability. They are also comparable or better hydrotropes for surfactants, especially nonionic alkoxylates, and combine the improved biodegradability and good hydrotropy with a surprisingly large contribution to the cleaning performance of cleaning compositions as well as a valuable dispersing effect.
The product (I) can be produced by reacting a) a reducing saccharide or an alkyl glycoside and b) a quaternary ammonium compound having the formula 
where R6 is independently an aliphatic group with 1-4 carbon atoms or xe2x80x94CH2CH2OH; R7, R8 and R9 independently are a group (AO)s, an aliphatic group with 1-24 carbon atoms or a hydroxyalkyl group with 2-4 carbon atoms; 1=0 or 1 and k=0 or 1, provided that the sum (k+xcexa3 1) is 1-3, preferably 1; and R, AO, s, X, n, n1, y and r have the same meaning as in formula I. The nitrogen atoms where k or l is 1 are quaternary and thus have a permanent positive charge. Since compounds II are rather hydrophobic due to a limited number of oxyethylene units, they exhibit no or only limited hydrotropic effects. Also the cleaning ability of compounds having the formula II is poor. The obtained reaction mixture contains essential amounts of both the cationic sugar surfactant I and the quaternary ammonium compound II. This product mixture can advantageously be used without any purification as a hydrotrope. Normally the ratio between the cationic sugar surfactant I and the quaternary ammonium compound II is from 1:3 to 9:1.
Suitable examples of the cationic sugar surfactants and the quaternary ammonium compounds are those having the formulae 
where R is an aliphatic group with 6-24, preferably 8-20 carbon atoms; R1 is an aliphatic group with 1-4 carbon atoms or the group C2H4O(G)p; G is a saccharide residue that is connected to the polyethyleneoxy chain by a glycosidic bond and p (the degree of polymerisation) is 0-10, preferably 0-5, xcexa3 p being 1-15, preferably 1-8; EO is an ethyleneoxy group; s is 0-12; xcexa3 s is 2-15, preferably 5-12; Z and z have the meaning mentioned in formula I and 
where R, R1, EO, z, Z and s have the same meaning as in formula III except that p in the group R1 is 0, respectively.
Suitable examples of hydrophobic groups R in formula 1-IV are: hexyl, 2-ethylhexyl, octyl, decyl, cocoalkyl, lauryl, oleyl, rape seed alkyl and tallow alkyl.
The cationic sugar surfactants III are easily produced by reacting a reducing saccharide and the quaternary ammonium compound of formula IV. The reaction mixtures containing essential amounts of both compound III and IV are preferably used as hydrotropes without any separation of the compounds, mainly because such a separation is a costly operation. The relation between cationic sugar surfactant and the quaternary ammonium compound could vary between 1:3 and 9:1, preferably between 2:3 and 9:1.
Cationic surfactants containing sugar residues are known by the publications DE 4 413 686 and JP 4-193891. In DE 4 413 686 surfactants containing quaternary ammonium groups are prepared by reacting glycosides with quaternary halogenated compounds or quaternary epoxy compounds. The linkage between the sugar residue and the cationic part is an ether linkage. The products could also be prepared by first reacting the glycoside with a halogenated compound followed by reacting with an amine. The applications for these products are for example as components in detergent mixtures.
In JP 4-193891 cationic sugar surfactants are prepared by the following procedure: A reducing saccharide or an alkyl glycoside is reacted with a polyalkyleneglycol halohydrin in the presence of an acid catalyst to obtain a polyoxyalkylene halohydrin glycoside. This product is further reacted with an amine compound, whereby the chlorine is displaced, and the resulting amine is then quaternized by e.g. methyl chloride or dimethyl sulphate. The quaternization could also take place by directly reacting the halogenated intermediate with a tertiary amine.
These products are used as mild surfactants with good biodegradability. However, the procedure of making them requires the production of the intermediate polyalkyleneglycol monohalohydrin where the starting material is 2-chloroethanol, which nowadays is only produced on a small scale and further is a highly toxic and irritant substance. To obtain the polyalkyleneglycol monochlorohydrine, the 2-chloroethanol is alkoxylated in the presence of an acid catalyst. The glycosidation process which then follows, makes use of a laborious and costly work-up procedure with distillation or solvent extraction, which is performed in order to get rid of the unreacted polyalkyleneglycol halohydrin.
The process involves at least the following steps; preparation of the polyalkyleneglycol halohydrin, preparation of polyoxyalkylene halohydrin glycoside and at last preparation of the quaternary ammonium alkylaminopolyoxyalkylene glycoside by reaction with a tertiary amine. If a primary or secondary amine is used instead, additional steps are required to obtain a quaternarization. Furthermore, in the last mentioned case inorganic salt is produced, which is removed by filtering the product.
The present invention utilizes a different synthetic route to obtain cationic sugar surfactants. The general procedure for making products with the formula I according to this invention involves the one-step reaction between a quaternary alkoxylated ammonium compound II and a reducing saccharide or an alkyl glycoside. The compound II is obtained by standard procedures known to those skilled in the art. The reaction between II and the saccharide is a glycosidation and can be performed as follows: Compound II is heated to a reaction temperature of from 85 to 120xc2x0 C. and the saccharide is added in an amount of between 0.5 and 12, preferably between 1.5 and 6 mole saccharide/mole quaternary ammonium compound. Depending on the amine used, the cationic sugar surfactant I can contain one, two, three or more saccharide residues (G)p, where G and p have the meaning mentioned in formula I. The saccharide reactant is preferably added in excess with regard to the number of glycoside bonds desired, since the saccharide also has a tendency to condensate with more saccharide units. This condensation is indicated in the formulae by the polymerisation degree p. The reaction is catalyzed by strong acid, e.g. p-toluenesulphonic acid or sulphuric acid, which may be added to the reaction mixture in an amount of between 0.1 and 4, preferably between 0.7 and 2.1 mole % of compound II. If the compound II is reacted with an alkyl glycoside, the process is a trans-glycosidation reaction. To aid the removal of water or alcohol from the reaction mixture, the process is carried out under reduced pressure (50-70 mbar). The reaction time is very dependent on the temperature and varies between less than one hour to six hours. When no more water or alcohol distills off the product is neutralized.
The method for producing the cationic sugar surfactant of this invention is quick and convenient. The starting materials are readily available and the process does not require any work-up of the reaction mixture. There is no need to add an excess of the quaternary ammonium compound in the glycosidation reaction. Rather the saccharide or alkyl glycoside is added in excess to give products with several saccharide units attached.
In aqueous alkaline solution the cationic sugar surfactants according to the present invention exhibit excellent hydrotropic effects for surfactants like nonionic alkoxylates. These alkoxylates could contain a hydrophobic group of 8-50 carbon atoms, which preferably is a hydrocarbon group or an acyl group containing from 8 to 24 carbon atoms. Suitable examples of such nonionic surfactants are alkylene oxide adducts obtained by alkoxylation of an alcohol, an amine or an amide. One example is compounds having the formula
Rxe2x80x2O(AO)aHxe2x80x83xe2x80x83(V)
wherein Rxe2x80x2 is a hydrocarbon group having 8-18 carbon atoms, a is from 2-12, preferably 3-10, and AO is an alkyleneoxy group having 2-4 carbon atoms, the number of ethyleneoxy groups being at least 50% of the total number of alkyleneoxy groups. The Rxe2x80x2 group may be branched or straight, saturated or unsaturated, aromatic or aliphatic. Examples of hydrocarbon groups Rxe2x80x2 are: 2-ethylhexyl, octyl, decyl, cocoalkyl, lauryl, oleyl, rape seed alkyl, tallow alkyl, octylphenol and nonylphenol. Especially suitable hydrocarbon groups are those obtained from oxoalcohols, Guerbet alcohols, methyl substituted alcohols with 2-4 groups having the formula xe2x80x94CH(CH3)xe2x80x94 included in the alkyl chain, and straight alcohols.
Another example of suitable nonionic surfactants are compounds having the formula 
wherein Rxe2x80x3 is a hydrocarbon group or an acyl group having 8-18 carbon atoms, AO has the same meaning as in formula V and the sum of b1 and b2 is 2-12, preferably 3-10. The hydrocarbon group and the acyl group can be aromatic or aliphatic, branched or straight, saturated or unsaturated. Examples of suitable groups are 2-ethylhexyl, octyl, decyl, cocoalkyl, lauryl, oleyl, rape seed alkyl, tallow alkyl and the corresponding aliphatic acyl groups. If Rxe2x80x3 in the formula VI is an acyl group, preferably one of b1 and b2 is 0, whereas if the nitrogen atom is an amine nitrogen, b1 and b2 are both preferably different from zero.
The cationic sugar surfactants of the invention are normally used in alkaline compositions having a pH-value above 8, preferably from 9-13, for use in the cleaning of hard surfaces, like degreasing of metal and plastic, dish washing and car washing. A suitable formulated composition concentrate may contain
a) 0.5-20% by weight of a surface active nonionic alkylene oxide adduct,
b) 0.2-20% by weight of a mixture consisting of a cationic sugar surfactant according to formula I, and a compound of formula II present in a weight ratio of from 1:3 to 9:1,
c) 0.5-30% by weight of alkali and/or polyelectrolytes like alkaline complexing agents,
d) 0-10% by weight of other conventional components in cleaning compositions, like other surfactants, other hydrotropes, thickening agents, solvents, colorants, soil antiredeposition agents, defrosting stabilizers, preservatives, corrosion inhibitors, foam regulators, etc., and
e) 30-98.8% by weight of water.
The concentrates are normally diluted with water prior to use, and the ready-to-use solution may be diluted to a concentration of from 0.05% to 15% by weight of alkali and/or alkaline complexing agents.
The complexing agent in the concentrate can be inorganic as well as organic. Typical examples of inorganic complexing agents used in the alkaline cleaning concentrate are alkali salts of silicates and phosphates, such as sodium tripolyphosphate, sodium orthophosphate, sodium pyrophosphate, sodium phosphate, polymer sodium phosphates and the corresponding potassium salts. Typical examples of organic complexing agents are alkaline aminopolyphosphonates, organic phosphates, polycarboxylates, such as citrates; amino-carboxylates, such as sodium nitrilotriacetate (Na3NTA), sodium ethylenediaminetetraacetate, sodium diethylenetriaminepentaacetate, sodium 1,3-propylenediaminetetraacetate and sodium hydroxyethylethylenediaminetriacetate.
The following examples are illustrative of the invention and are not to be construed as limiting thereof.
In Examples 1-5 the production of some representatives of the quaternary sugar surfactants of the present invention is described. In Example 6 the improved biodegradability of the quaternary sugar surfactants as compared to prior art hydrotropes is demonstrated. In Examples 7 and 8, it is shown that the cationic surfactants of the present invention are better hydrotropes than the cationic hydrotropic compounds of the prior art both with respect to the amount of hydrotrope needed to obtain a clear solution with given concentrations of nonionic surfactant and alkaline complexing agents, and with respect to the amount of complexing agent possible to include in an isotropic alkaline cleaning concentrate. In Example 9 the improved cleaning ability as compared to prior art hydrotropes is demonstrated.